REAPER development is led by Justin Frankel, who also created Winamp and the Gnutella peer-to-peer file sharing network.

[4] Version 2.0 (October 2007) included a more sophisticated user interface, an extended mixer, and the ability to save and load screen layouts.

This update also added the Zplane Elastique 2 algorithms for enhanced time-stretching and pitch shifting, supported Windows and Mac OS and remained compact enough to run off a USB memory stick.

[5] Version 3 (2009) added nested tracks, plugin controls in the mixer, VCA grouping and enhanced automation and MIDI features.

[6] Version 4 (2011) continued Cockos' reputation of "listening and involving their user base with frequent updates, beta versions and forum discussion"[7] while adding features such as automatable pitch shift envelopes, multichannel setups such as quad, 5.1, 7.1 and 9.1, improved project management and window arrangement customization.

Version 5 (2015) added video editing capability, automation of individual effect parameters, enhanced scripting and VST3 support.

[8] Version 6 (2019) introduced Retina, HiDPI and Metal display support for higher resolution and faster screen redraw, FX plugin embedding for faster workflow, MIDI CC envelope automation, a graphical patchbay and performance improvements for projects with 200+ tracks.

The included plug-ins are also accessible as a standalone download for users of other DAWs as the "ReaPlugs VST FX Suite".

[17] Also included are hundreds of JSFX plug-ins[18] ranging from standard effects to specific applications for MIDI and audio.

JSFX scripts are editable text files,[19] which when loaded into REAPER (exactly like a VST or other plug-in) become full-featured plugins ranging from simple audio effects (e.g delay, distortion, compression) to instruments (synths, samplers) and other special purpose tools (drum triggering and surround panning).

It supports common video effects such as fades, wipes, cross-fades, opacity, motion detection and text titles.